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Low Fat Diet and Sunscreen: a Recipe for Disaster (mit.edu)
47 points by bayareaguy on Oct 13, 2008 | hide | past | web | favorite | 59 comments

Ignoring the window dressing about the health risks of extreme low-fat diets (which are real, and there's plenty of better writeups on them) this is an article about Vitamin D. And the question you have to ask when you see an article like this is: What's the groundwork-to-hysteria ratio? I see plenty of hysteria here, but no data. There's one cited reference to the scientific literature... but it's on a different subject.

There's nothing wrong with hypothesizing that (a) modern medical practices are leading to deficiencies in Vitamin D among certain populations and (b) Vitamin D deficiency is linked to autism. But the responsible next step is to get some good data, or at least link to some. It's not to write stuff like this:

Since the 1970's, our country has witnessed a 3000% increase in the sales of sunscreen products, alongside a 30% increase in deaths from melanoma[17]. Isn't it time to admit that sunscreen is not working?

This is a telling paragraph. It tells me that the author is prone to making mistakes straight out of Darrell Huff's How to Lie With Statistics: Clock A strikes midnight a few seconds before clock B; isn't it time to admit that A caused B to strike?

Autism seems to be one of those issues that really inspires the quack epidemiologist. When you combine it with the opportunity to lecture new mothers -- our culture's favorite vice -- the temptation becomes irresistable. But it's worth remembering that actual epidemiology is really hard. Diagnosing autism without bias is hard. Randomly sampling the population for autism is even harder. Even something relatively simple, like measuring Vitamin D levels in the blood, is tedious and expensive and difficult to do without bias. But just because anecdotes and handwaving are much easier doesn't make them more believable.

> How to Lie With Statistics

There is no fallacy in the statement you've focused on. I'm a bit confused. Sunscreen is sold and used to prevent cancer. There's no evidence it has, and sound reasons to suggest sunscreen has contributed to cancer. That's all it's saying.

> Diagnosing autism without bias is hard.

Are you suggesting the autism epidemic is a product of better diagnosis? If so, where are all the autistic 50 year olds?

Do I have to spell it out?

The observation is that sunscreen sales and melanoma rates are correlated. That's probably true, but it doesn't tell us anything about causation, one way or the other. Perhaps sunscreen is ineffective against melanoma. Or perhaps melanoma rates are rising because sunscreen use causes melanoma. Or perhaps sunscreen sales are rising because melanoma rates are rising. (As someone who has just watched a close relative die of metastatic melanoma, I assure you that the experience really inspires you to wear sunscreen and go to the dermatologist. Every time I get a pimple, I have to fight the desire to visit the emergency room.)

Perhaps sunscreen sales and melanoma rate would be completely unrelated, if they weren't both driven by an external cause. Perhaps they're both caused by population increases in the Sun Belt, or by other demographic changes.

Perhaps sunscreen is highly effective against melanoma, but there are still lots of older patients who got all their sun in the 1940s, 50s, and 60s before sunscreen was invented, and those patients are still getting melanoma at large rates. Or perhaps sunscreen is completely ineffective, but we won't know until the people who used it as kids reach their sixties. Or perhaps sunscreen causes melanoma... but it takes more than fifty years to do so.

Perhaps sunscreen causes autism! I guess that's what this article is trying to suggest.

As you can see, pulling hypotheses out of one's ass is easy to do, and it's fun for the whole family. It's also uninformative. Scientific studies would be informative. I'm sure there are lots and lots and lots of published studies which address hypotheses like these. It's a pity that the article didn't cite any of those studies.

It seems likely, at least, that sunscreens are ineffective against melanoma. Via a link on the Slip-Slop-Slap Wikipedia page (http://en.wikipedia.org/wiki/Slip-Slop-Slap):

"While few epidemiologic studies have examined the relationship of sunscreen use and skin cancer, two studies suggest that sunscreens may not be effective in preventing skin cancer. A large case-control study showed higher risks of melanoma in men who used sunscreens, and a large prospective study showed a higher incidence of basal cell carcinoma in women who used sunscreens. The excess risks in the latter study persisted after multiple adjustment for differences in skin type and time spent outdoors."

-- "Could Sunscreens Increase Melanoma Risk?" http://www.ajph.org/cgi/reprint/82/4/614

Hooray, links to data!

This is from 1992 and earlier, though. One wonders if there has been any more progress in recent years.

And here is where I get to rant about my own pet peeve: Why should I be surprised that so few people know how to properly cite scientific literature? That literature is locked behind paywalls! I'm not going to even bother using PubMed on this, and it's only partly because I don't care. It's mostly because, even if I turn up a definitive set of review papers in Nature on this very topic, I won't be able to read them without paying $15 each, or whatever.

I'm not sure if you are referring to the article I quoted or to its references... but the page that I linked to let me download the article directly for free, despite a sidebar link that purportedly also allows you to purchase the article. (I was surprised, too.)

I, too, wonder if there aren't more recent studies. The two studies cited were from 1985 and 1990, though; if that's the most they could come up with in 1992, it sounds like the area is sparsely researched.

The references, of course. It's hard to operate without them. Particularly when you're outside of your own field, and can't just name the various schools of thought -- and the major authors and manuscripts associated with them -- off the top of your head.

If you want to dismiss correlation altogether you should really just argue that all medical research and discussion is useless (which I wouldn't consider an absurd position). You can tear apart pretty much any correlation backed assertions with "what-ifs." One simply must be reasonable.

If sunscreen sales clearly negatively correlated to melanoma, that would be a point worthy of consideration in this discussion, no? It is reasonable to consider this lack of correlation as a piece of evidence in support of the discussed framework. Apply your own grain of salt: this is not a scientific publication and the audience is assumed to be a reasonable person.

There would be practically nothing to say in the "non-sciences" (medicine, economics, etc.) if one were not allowed to admit "circumstantial evidence."

I'm not dismissing this correlation. I was even generous enough to assume that it's not being made up. (Only half of it is cited, and the citation is to a Newsweek article which has no footnotes of its own.)

I'm just finished with it. It doesn't have much explanatory power. It fits a big universe of hypotheses, some of which I have outlined above. It's provocative, which is not the same thing as conclusive. But consider me provoked. I'm curious. Bring on the science.

Until someone brings some more studies to the table there's really not much more to say. I'd rather spend my afternoon getting some carefully modulated sun exposure. ;)

The problem is that the author assumes that the increasing rate of cancer is due to ineffective sunscreen. But there are many other possible causes: For one, the use of sunscreen may give people a false sense of security, leading them to stay out in the sun longer than they would without sunscreen. Also possible is that advances in healthcare are allowing people to live much longer on average, which in turn has affected statistics as cancer becomes a larger problem to deal with among the elderly.

Another possibility is that the rise in melanoma and the increase in sunscreen use are caused by the damage to the ozone layer and the corresponding social alarm, respectively. We have mostly forgotten about the ozone layer, but it was a hot topic not so long ago.

OTOH, some 10 years ago, some sunscreen makes were forbidden (at least in Spain) because a component in them (I can't recall the name) had been proven to cause melanoma.

> there are many other possible causes

Circumstantial evidence is court admissible.

So? Circumstantial evidence may be admissible in court, but particularly in science, it is not sufficient.

This is weak evidence. I would be more convinced by a controlled experiment. Do a study where two demographically equivalent groups are given equal sun exposures one with sunscreen the other without, and then compare their rates of melanoma. The author doesn't have data on sun exposure or evidence that the sunscreen sold is actually used, etc. etc.

Are you suggesting the autism epidemic is a product of better diagnosis? If so, where are all the autistic 50 year olds?

The autism "epidemic" is largely being caused by an expansion of the definition of autism. Hence, lots of young people with Asperger's, and other mild autisms, but not many 50-year-olds. They're not being diagnosed. (Whether Asperger's is an actual syndrome or just a product of upbringing and personality type: that's a different argument. I tend toward the latter -- I am skeptical about its existence at all.)

Asperger's is a syndrome - that is, a condition defined and diagnosed only by reference to its symptoms. Doubting that there is a single underlying cause is valid, and not even terribly controversial - one of the two psychs who diagnosed me (earlier this year; I'm in my mid-30s) told me that she could buy that as a label it could apply to half a dozen or more underlying causes. But doubting that it's a syndrome is... well, a bit silly. :)

Not quite, a syndrome is a set of correlated symptoms.

Basically, consider the sumptoms of deafness, impotence and tingling in the hands and feet (D, I and T). Suppose that deafness, impotence and tingling are all independent of each other (P(D | I) = P(D)). In this case, there is no syndrome. If, however, they are strongly correlated(P(D | I) >> P(D)), we have a syndrome.

Basically, "deaf and impotent provides no information about tingling" == no syndrome.

"Deaf and impotent implies a high probability of tingling" == syndrome.

As described in the article, autistic people are almost completely dysfunctional. Have you ever met one? It's a bit ridiculous to suggest full blown autism was occurring at current rates, which are having serious public school budget impacts, in the past and nobody noticed. And even more ridiculous to suggest that nobody has bothered to look for all these previously undiagnosed adult autism sufferers, who would have to still be living with their parents or institutionalized.

I don't think it is inconceivable that the adult autism sufferers remain undetected. Presumably, their lives are already arranged. Either they survived somehow, or they didn't. If they survived, there probably is some kind of routine that keeps them alive (maybe an institution, or they live as beggars on the street, or whatever). In that case, why should somebody check up on them again? Sure, it would be nice if somebody would, but why should it happen? When was the last time you learned about some new medical breakthrough and thought "hey, let's go out on the street and check all homeless people to see if they have this condition"? (Not saying older autistic people are homeless, I have no idea how they survive once their parents are dead). Also, there is no cure for autism (or is there?), so simply correcting the diagnosis might not help the older autistic people much (at least not "help" in terms of making it easier for the people they live with - might be easier for themselves, though). Maybe now they are simply sedated with powerful drugs most of the time and don't do much.

Anyway, the main point remains: be careful with "common sense" conclusions.

If they're suggesting that the rise of full-blown autism has somehow risen to epic proportions, they're statistically incorrect. I think they're including milder forms and pretending they're all the same.

At McDonald's for lunch today. Well, I doubt "all", but definitely "plenty".

Unfortunately adult autism care in the US is fairly deplorable.

Umm, this is a true story. There was a group there, being helped by 2 or 3 escorts for one of their daily or weekly activities. I wasn't insulting employees of McDonalds. If the parent poster isn't seeing adult mentally handicapped, s/he is not looking very hard.

Assuming this woman doesn't own a chain of tanning salons as her side gig - it's a good read. An interesting alternative to the current opinions on vitamin D, Autism and low-fat diets.

As I read it, I quickly categorized it as an interesting persuasive essay citing supporting facts. I have no problem reading papers like this and gaining what I can from them. There is a place for persuasive essays and a place for research papers. As long as the author is not trying to misrepresent - no problems.

I read up on the author a bit and she seems to be closer to an expect on these issues than a vast majority of op-ed diet and autism write-ups that I've seen. Plus she's got an undergrad biophysics degree to boot.


The author reads like a kook, but the good thing is that they put forward a testable hypothesis (that vitamin D deficiency causes autism, or at least increases the risk of it) so it should be either confirmed or disproved by further studies.

The author reads like a kook, but the good thing is that they put forward a testable hypothesis

Anybody can put forward a testable hypothesis. That doesn't make you a good scientist.

A good scientist is one who puts forward a testable hypothesis and then tests it before publishing.

A great scientist is one who creates a testable hypothesis, tests it, and then -- when the data fail to prove the hypothesis -- shrugs, publishes the definitive refutation of her own hypothesis, and moves on to something else. It took me years to realize just how rare a skill this is, even for scientists. Part of the problem is that the career system for scientists actively discourages this -- once you've finally managed to sell a line of research to a funding agency, there are very strong incentives to keep that research going, even if it isn't getting anywhere.

Agreed. The hypothesis is interesting, but the phraseology and assembly of info reads a bit like a kook.

But as you say - it's a testable hypothesis, so I don't care how it's been written up, it would be good to test this.

It's already researched to hell. This has been clear from the evidence for a long time now. It just contradicts the dogma.

See the para near the end: "However, I will concede that thus far there is no definitive study that would leave no doubt that this hypothesis is correct. This, more than anything else, is what's needed to really convince people to dramatically change their practices"

Have the studies also been published exclusively in hell, or can you provide a citation?

Rules to live by:

1. If someone feels the need to point out, at the end of an essay, that they have a PhD, they're probably a kook.

2. That goes doubly for anyone who feels the need to tell you which prestigious institution their PhD is from.

This article is interesting, but I cannot take it seriously until the sources begin to link to more supporting medical literature. Nearly half of the links are to a website with a domain specifically selling this message. I clicked around this site and didn't find any citations.

I'm sorry, but the format of this site trips off my whackjob detector and no one should be willing to take random medical advice without at least the appearance of support from the medical literature.

This is doubly true when it comes to subjects of fertility or diet.

Some economists are causing tons of trouble by using economic-style research design to show autism rates are linked with cable television and the rain. Certainly tv watchers in rainy city washington are going to get less sunlight, so that adds more credence to her argument.

Their study:


> economic-style research design

If you sample 100 uncorrelated variables looking for significance at 95% confidence, you should find about 5 which are significant.

Data mining to produce hypotheses is fraught with danger. You should declare your hypothesis and then go to the data, otherwise your confidence measurement is bogus.

Doubling of vitamin D for children is urged: http://www.nytimes.com/2008/10/13/health/policy/13vitamind.h...

That trip to Mexico at the 'all you can eat' resort my wife and I took when she was 6 months pregnant suddenly looks like brilliant vacation planning.

It's not a question of eating a lot. Gorging on pasta when pregnant will just produce a type I diabetic child. The issue is animal/fish fat consumption. Women and children need quite a bit of it.

It was a joke, but I'm enjoying the responses.

High pasta diets are not exactly on the menu in Mexico.

"Gorging on pasta when pregnant will just produce a type I diabetic child."


Seriously, is there study that show a low-fat/type I diabetes connection?

I think it's more of a high-carb/diabetes connection.

The issue is in utero insulin exposure.


When mom eats french fries and rice the insulin spikes permanently screw up the kid's endocrine system, leaving a propensity to obesity if not diabetes.

Do you mean Type I or Type II? Everything I've read indicates that the cause of type one isn't clearly understood, but is likely an autoimmune condition. However, conditions that lead to obesity later in life can lead to type II diabetes.

Are the obesity rates in countries with diets high in rice consumption (e.g. Japan) especially high? Or is it usually offset by something (so in Japan's case: fish consumption)?

Living in Tokyo, an obese person really sticks out. You just almost never see them. You do see some fat teenagers though, since they are abandoning the traditional diet.

Japan is in love with fat in all its forms (fatty marbled beef, fatty tuna, fatty pork) and there is almost no culture of sun-screen usage, but they also are much better at producing melanin than europeans, making for pretty effective natural protection.

They also have one of (if not the) largest populations of centenarians on earth.

Gorging on pasta when pregnant will just produce a type I diabetic child.

I think you meant "Type II".

True, this article immediately fails Sagan's bullshit detector. Claiming you understand _any_ cause of autism is an extraordinary claim if there ever was one.

In conclusion: never trust a doctor without verifying things on your own. Doctors are no smarter than the financial professionals who have obviously got things disastrously wrong lately.

Well, I disagree with that generalisation. A good doctor makes decisions based on evidence (symptoms of the patient, proven effect of the treatment) as well as experience as a doctor.

When "verifying things on your own" you run into all kinds of unfounded and delusional ravings on the internet. Doctors may err on the side of conventional wisdom, but that's not a call to disregard them and err on any nonsense that you come aross.

Then why do most doctors reject evidence based medicine?

Do most doctors reject evidence based medicine? Do you have a reference or citation for that assertion?

I presume you're talking about "evidence based medicine" the right wing medical reform movement, not all medicine based on evidence. Because while many doctors reject that movement, few seem to reject using evidence to pick treatment regimes.

Is it really right wing? Why? I've just read multiple articles about how slow Dr's are to adopt it even though, empirically, it is more effective. I figured they rejected it for the same reason people always reject things: "that's the way we've always done it".

Now granted, those articles could have been biased, but I had no idea there was any sort of left wing vs right wing thing going on. Stupid politrix.

The entire movement reminded me of Moneyball by Michael Lewis.

There are, of course, a few doctors who reject the very idea that mere scientific evidence should be able to tell them what to do. But in general, most doctors want to provide the best care they can for their patients, and that includes scientific evidence.

However, it's extremely common for doctors to prescribe medicine off-label, before the full level three trials have completed for that use (which can take a decade). There is often compelling evidence a medicine is effective (in the Bayesian sense) far before there is official "Evidence" which counts for "Evidence Based Medicine".

The very fact that it's called "Evidence Based Medicine" should set off alarm bells. Being against it sounds like being against science in medicine, which would just be stupid. In fact, it's code for "restrict public care facilities from being able to offer a full range of medical benefits to conserve money".

Thanks for the information. I seriously thought it was much more like the Moneyball situation where it was just a bunch of old schoolers not accepting reality & empirical evidence and instead relying on standard practices and conventional wisdom.

P.S. We just fully implemented Twisted at TicketStumbler :) (I heard you guys use it, and love it, at Justin.TV).

I'm sure there's some of that too :).

Twisted really is awesome; we've been super happy with it. A little sad they wouldn't take our memcache get_multi patch (they said we hadn't written enough tests for it).

"Evidence-based medicine (EBM) aims to apply evidence gained from the scientific method to certain parts of medical practice." - wkipedia.

What on earth is "right-wing" about that?

Nothing! But many right wing policies are pushed in the name of EBM; in practice it's been used to cut down on medical options for the poor.

Everyone should of course be for applying scientific evidence to medical practice.

Is that a feature of USA'ian health politics (which I don;t follow that closely), or does it happen here in the Uk too?

This is complicated by the fact that most doctors don't know jack squat about statistics. Since most medical data nowadays is collected through statistical means you end up witht he embarrassing situation where a economist or a mathematician would be better informed about a subject if it were not for the constant attention a doctor pays to it.

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